Novel wastewater recovery process for sustainable sodium carbonate production with CO2 and SOx utilization

Abstract

Ammonia-soda process, which produce soda ash, emits flue gas containing a large amount of CO2 and SOx. The wastewater discharged from the ammonia-soda process contains cations, such as Na+ and Ca2+, which can be recovered and reacted with a CO2 and SOx. In this study, we designed a CO2 and SOx utilization process for the sustainable production of sodium carbonate using wastewater recovery system, extracting Na+ and Ca2+. The proposed process involved the following steps: (1) metal-ion separation, which produces NaOH and Ca(OH)2; (2) capture and utilization of SOx using Ca(OH)2; and (3) capture and utilization of CO2 using NaOH and Ca(OH)2, respectively. The economic feasibility of the proposed process was verified by comparing its total annualized cost (TAC) with those of conventional processes. Approximately 99% of SOx was captured to produce high-purity desulfurized gypsum, and 99% of CO2 was captured to be transformed into CaCO3. To confirm the CO2 reduction of the process, the carbon dioxide equivalent (CO2e) was calculated by evaluating the amount of greenhouse gases. The CO2e decreased to 71.4% compared with that of the conventional process. The TAC of the proposed process decreased by 10.67% and 19.63% compared with that of the ammonia-soda and Hou processes, respectively. Thus, this study proposes an industrially potential process design for sustainable sodium carbonate production by utilizing CO2 and SOx with wastewater recycling, without additional reactants, making it more economically viable.

Keywords

• Desulfurization gypsum
• Ammonia-soda process
• SOx capture
• CO2 utilization
• Wastewater